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copied!<p>After some reading, writing and testing I got something:</p> <pre><code>function inc(&$var){ if (isset($var)) $var++;else $var=1; } </code></pre> <p>and thought I struck gold, but let's see the tests first...</p> <h2>Test code:</h2> <pre><code>$a=array(); // Pre-Fill array code goes here for($i=1;$i<100000;$i++) { $r=rand(1,30000); //increment code goes here } // Remove extra keys from array with: //foreach ($a as $k=>$v) if ($v==0) unset($a[$k]); </code></pre> <p>Execution times: <em>(for informative purposes only)</em></p> <pre><code>inc($a[$r]) 1.15-1.24 @$a[$r]++ 1.03-1.09 $a[$r]=array_key_exists($r,$a)?$a[$r]++:1; 0.99-1.04 $a[$r]=!empty($a[$r])?$a[$r]++:1; 0.61-0.74 if (!empty($a[$r])) $a[$r]++;else $a[$r]=1; 0.59-0.67 $a[$r]=isset($a[$r])?$a[$r]++:1; 0.57-0.65 if (isset($a[$r])) $a[$r]++;else $a[$r]=1; 0.56-0.64 //with pre-fill $a=array_fill(0,30000,0); +0.07(avg) for($i=1;$i<=30000;$a[$i++]=0); -0.04(avg) //with pre-fill and unset $a=array_fill(0,45000,0); +0.16(avg) for($i=1;$i<=45000;$a[$i++]=0); +0.02(avg) </code></pre> <h2>Conclusions:</h2> <ul> <li><code>@</code> is of course the fastest to type and I don't see any problem in using it <strong>in this case</strong> but feel free to check this question also: <a href="https://stackoverflow.com/q/136899/731947">Suppress error with @ operator in PHP</a></li> <li>completely suppressing errors (before the loop and enabling errors after the loop) via <code>ini_set()</code> is worse than all on performance</li> <li><code>inc()</code> looks nice and clean, easy to type and does checking instead of suppressing, but calling it looks to be even slower than <code>@</code></li> <li><code>isset()</code> is slightly faster than <code>empty()</code>, but both perform fairly the same</li> <li>interestingly using <strong>shorthand</strong> <code>if</code> statements is <strong>slightly slower</strong>!</li> <li>best results achieved when pre-filling the array. Even if length is unknown a good prediction would be still slightly faster on a huge dataset</li> <li>strangely, <code>array_fill()</code> takes slightly longer than <code>for</code> ?!?!</li> </ul> <h2>RFC</h2> <p>I don't consider this answer 100% complete, although, for now it looks like <code>isset()</code> is the fastest and <code>@</code> the laziest.<br> Any comments and ideas are appreciated!</p>

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